A rare case of placental mesenchymal dysplasia (PMD) in a 26-year-old patient is reported. Ultrasound scan at 17 weeks of gestation showed placenta with multiple cystic spaces and a normal appearing fetus. Following delivery of a term live baby, histological examination of the placenta was suggestive of PMD. The early recognition of this rare condition by characteristic ultrasonographic findings is herein emphasized and hence that PMD is distinguished from molar pregnancy.